What_Would_Jimi_Do:i have a friend that had these 2 huge oscars. put your hand(s) above the tank and they catch you also.

I've had that happen before. For years, they were happy chomping at the air bubbles trapped in my arm hair as I was cleaning their tank. Then one day, one of them chomps my pinky. Their teeth were too tiny to really break the skin, but it did make it impossible to pull them off without harming them. Eventually they release. Became a PITA to clean the tank, though. Feeding them in advance to sate their appetite didn't work. I eventually had to chase them around the tank with my hand to teach them that "hand is bad".